Ok. From what I could gather.
It's Rie's "baby", the first project she "spearheaded all on her own", she wrote the pitch and send it to the Fish. There were a lot of meetings with the Idol Showdown team (so if not directly involved they gave permits, I assume). There will be a talent tournament and a fan tournament. Music, art, planning, etc was done by her. She's not gonna be a fighter but the commentator.
No mention of sprites, but the stream was before those starting appearing on Twitter, next Phase Weekly will have a segment to explain the rest.
Hats off to Hime on this one.